Cadaverine is Transported into Vibrio vulnificus Through its CadB in Alkaline Environment

摘要

The exogenously added cadaverine is effective in protectingVibrio vulnificus from methyl viologen (MV)-inducedsuperoxide stress at pH 8.5. Such a protective effect bycadaverine was not observed at pH 7.5. Consistently, theaccumulated level of intracellular cadaverine at pH 8.5 isapproximately four times as much as that of the controlcell at pH 7.5. Cadaverine accumulation is not affected byMV. The protection of V vulnificus by cadaverine fromsuperoxide stress was abolished when cadB coding for thelysine–cadaverine antiporter was interrupted. However,the cadaverine-mediated protection was complementedwith cadB DNA. Therefore, CadB of V vulnificus not onlyacts as a lysine–cadaverine antiporter at acid pH toneutralize the external medium, but also mediates cadaverineuptake at alkaline pH to result in cell protection fromsuperoxide stress.